Nicene and Post-Nicene Fathers, Vol. III:
Moral Treatises of St. Augustin: Section 22

22. What then, if a homicide seek refuge with a Christian, or if he see where the homicide have taken refuge, and be questioned of this matter by him who seeks, in order to bring to punishment a man, the slayer of man? Is he to tell a lie? For how does he not hide a sin by lying, when he for whom he lies has been guilty of a heinous sin? Or is it because he is not questioned concerning his sin, but about the place where he is concealed? So then to lie in order to hide a person’s sin is evil; but to lie in order to hide the sinner is not evil? “Yea, surely:” says some one: “for a man sins not in avoiding punishment, but in doing something worthy of punishment. Moreover, it pertaineth to Christian discipline neither to despair of any man’s amendment, nor to bar against any man the way of repentance.” What if thou be led to the judge, and then questioned concerning the very place where the other is in hiding? Art thou prepared to say, either, “He is not there,” when thou knowest him to be there; or, “I know not, and have not seen,” what thou knowest and hast seen? Art thou then prepared to bear false witness, and to slay thy soul that a manslayer may not be slain? Or, up to the presence of the judge wilt thou lie, but when the judge questions thee, then speak truth that thou be not a false witness? So then thou art going to slay a man thyself by betraying him. Surely the betrayer too is one whom the divine Scripture detesteth. Or haply is he no betrayer, who in answer to the judge’s interrogation gives true information; but would be a betrayar, if, unasked, he should delate a man to his destruction? Put the case with respect to a just and innocent man, that thou know where he is in hiding, and be questioned by the judge; which man, however, has been ordered to be taken to execution by a higher power, so that he who interrogates is charged with the execution of the law, not the author of the sentence? Will it be no false witness that thou shall lie for an innocent man, because the interrogator is not a judge, but only charged with the execution? What if the author of the law interrogate thee, or any unjust judge, making quest of an innocent man to bring him to punishment? What wilt thou do? wilt thou be false witness, or betrayer? Or will he be a betrayer, who to a just judge shall ultroneously delate a lurking homicide; and he not so, who to an unjust judge, interrogating him of the hiding-place of an innocent man whom he seeks to slay, shall inform against the person who has thrown himself upon his honor? Or between the crime of false witness and that of betrayal, wilt thou remain doubtful and unable to make up thy mind? Or by holding thy peace or professing that thou wilt not tell, wilt thou make up thy mind to avoid both? Then why not do this before thou come to the judge, that thou mayest shun the lie also? For, having kept clear of a lie, thou wilt escape all false witness; whether every lie be false witness, or not every: but by keeping clear of all false witness in thy sense of the word, thou wilt not escape all lying. How much braver then, how much more excellent, to say, “I will neither betray nor lie?”